Improved machine for grinding- and polishing slate



datul @Quatre HENRY ARPER, OF BERLINSVILLE, PENNSYLVANIA.

Letters Patent No. 95,342, dated September' 28, 1869, antedated .March29, 1869.

`IMIPROVIEII'J MACHINE FOR GRINDIN G- AND P OLISHING- SLTE.

The Schedule referred to in these Letters Patent and making paxt of thesame.

To all whom it 'may concern l Beit known that I, HENRY W. HARPER, ofBerl linsville, Northampton county, Pennsylvania, have invented anImproved Slate-Grinding and Polishing Machine; and I do hereby declarethe following to be a full, clear, and exact description of the same.

My invention relates to mechanism, fully described hereafter, forgrinding and polishing school-slates; and It consists-- First, o f ascrew, so arranged as to regulate the extent to which the slates have tobe reduced.

Second, in the combination of a pointer and graduated plate with thesaid screw, for the purpose of guiding the attendant in operating thesame.

. In order to enable others familiar with machinery of this class, tomake and use my invention, I will now proceed to describe itsconstruction and operation, reference being had to' the accompanyingdrawing, which forms a part of this specitication, and in which 4FigureV -1 is a'vertical section of my improved slategrinding and.polishing machine, and

Figure 2, a transverse vertical. section on'the line 1 2, tig. 1.

lh frame of the machine consists, in the present instance, of the` baseA, the four posts B B B B, and the cross-bars C C and D.

E and F are two vertical shafts, turning below in steps a on the base A,and above, in suitable bearings b on the cross-bar D.

lo the shaft E is secured a disk or wheel, G, having an annular recess,d, and a central projecting hub, e.`

The disk is surrounded by a metal ring,4 f, between which and the splitring h in the annular recessd, are confined the slates t', by means ofbolts j, both of the rings f and h projecting a short distance above theupper surface of the disk, but not so far as to reach the upper surfaceof the slate.

A yoke, H, (lig.1,) is secured to the opposite beams, C C, of the frame,and through this yoke passes a screw, fm, provided with a handle, n, theforked `short arm of a lever, I, (hung to a projection on the yoke)being adaptedto a groove formedat the upper end of the screw, and thelong arm serving as'a pointer for the graduated plate J o n the yoke.

To the upper end of the shaft F is securedfa disk, K, to the undersideof -which is attached a ring, L, composed ofvulcauized rubber orgutta-percha, combined with pulverized quartz or emery, the material ofwhich the well-known vulcanite emerywheels are composed, beingespecially applicable to the purpose.

The ring should beof such a diameter that its peripheryl will projectashort distance beyond the inner end of the slates on the disk G, asshown in gfl.

'lhe shaft E is permitted to have a limited vertical movement in itsbearings, and is vcontrolled by alever,

yM, connected toa standard, lq, on thebase A, the

forked portion of thelever passing between collars. t ton the shaft.

After loosening the'nuts of the bolts j, and thereby permitting thesplit ring h to contract, the slates@ are placed on the disk G, and theynuts are then tightened, so as to expand the ring, and thusconiine ltheslates between it and the outer ring f.'

The revolving shaft E, with its disk Gr, is tlen elevated,rso as. tocause the slates -to bear against the under surface of the rotatinggrinding-ring, which rapidly reduces them' to the desired level surface.

It is important that the upward movement of the shaft E should belimited, so as to prevent toolgreat a reduction of the slates', andprevent the rings f and h from coming in contact with thegrinding-surface.

-The height to which the slates have to be elevated, and the extent tolwhich they have to be reduced, may

-be regulated with precision, by turning the screw m,

the coinciding of the-pointer with certain predeter mined marks on thegraduated scale, guiding the .operator .in adjusting the screw.

I have found that a rapidly-'revolving emery-ring, L, ,has a Iuch bettereffect in reducing or polishing th slates on the revolving disk G, thana plain ginding-disk, the surface of the slates being more uniform andfree from scratches than when a disk is used., Y

Although I prefer to turn the disk G and the grinding-ring L in.contrary directions, the two may turn in ythe same direction,'thegrinding-ringvrevolvng rapid ly,and the disk for holding the slatesturning at a lowerrate of speed. l

The grinding-ring L may be secured to arms radiating from a central hubon the shaft F, instead of to tlledisk K.

It will be evident that more than one disk for holding the slates, andany desired number of grinding' or polishing-'rings may be applied tooneframe.

Without confining myself to any particular arrangement or .constructionof frame-work, or to any specific arrangement of gearing or belts fordriving the disks or rings,

I claim. as my invention, and desire to secure by Letters Patent- 1. Thescrew lm., arranged on the machine substantially as described, forregulating the extent ofthe re nesses.

H. WlVI. HARPER.

Vitnesses: I

' H. HoWsoN,

W. J. R.- DELANY.

